Mystery Sea Creature Invading Indian River Lagoon, Threatens Oysters

A mysterious sea creature of unknown origins has been found in Indian River Lagoon in Brevard County.

The creature that looks like bunched up bright red daisy petals is an ascidian, better known as a sea squirt. But exactly how it got into the lagoon and where it came from has researchers puzzled.

The only thing scientists know for sure is that it is overgrowing native oysters, a keystone organism for the health of the waterway as well as an important part of the local economy. And it may be part of an ugly trend.

University of Central Florida biologist Linda Walters has been monitoring the lagoon and helping to restore its oyster population for the past 14 years. She has since seen three other non-native species invade the lagoon putting it at risk.

Global warming may be partly to blame as water temperatures rise and create inviting environments for species that typically stay in tropical climates farther south. Some states are spending millions of dollars battling invasive marine creatures that use interconnected waterways to spread.

“This is not unique to Florida,” Walters said. “We’re seeing more and more aquatic nonnative species across the United States. They compete with native species and can disrupt the natural ecosystem. And that can have very real consequences.”

In Brevard, for example, if oysters can’t grow because of an invasive species, they can’t clean the lagoon. It’s estimated that one oyster filters five gallons of water a day.

The oysters also provide refuge to native species such as blue crab, shrimp and red fish that locals catch and sell. Without them, many other creatures’ food sources disappear. In the Indian River Lagoon, Walters has identified 149 species that rely on native oysters in a balanced ecosystem.

Eric Hoffman, a UCF evolutionary biologist who specializes in genetic variation of invasive species, is working with Walters. Together with a team of students and other scientists, they are working to trace the origins of each new species in the lagoon through careful detective work.

It’s essential to figure out each species’ origins if invaders are to be kept from wrecking havoc on U.S. waterways, researchers say – like putting together a giant puzzle over long period of time.

“Each time these organism make it into a new environment, there is a potential for them to establish themselves,” Hoffman said. “Sometimes we don’t see the damage for decades. Other times it is more immediate.”

For example, the zebra mussel has steadily been invading U.S. waterways since the late 1980s when it was found in the Great Lakes region. The mussels, which originated in Europe, attached themselves to cargo ships. Now, they have been spotted across North America, including New York, Illinois and even parts of Canada.

The Great Lakes region has spent millions trying to get rid of the mussels, which clog up pipes at utility plants, factories and water treatment facilities. These finger-like shellfish also are endangering industrial, agricultural and municipal water supplies and could become a costly nuisance for freshwater shipping, boating and clamming.

In Brevard County, Walters and Hoffman have studied three other non-native sessile – or fixed – species for the past five years. They are the green mussel, the charru mussel and the pink barnacle. All have been found growing on local oyster reefs, and they’ve spread as far north as South Carolina.

Grants from United States Department of Agriculture, the Indian River Lagoon National Estuary Program and The Nature Conservancy help the UCF team track the different species. The team will continue to monitor the Indian River Lagoon and 100 other waterways that they check twice every year to study the spread of non-native species.

Although it may take some time, they expect to solve the mystery of this latest invader.

“We are working on it,” said Sarah Cohen, an associate professor at San Francisco State University’s Romberg Tiburon Center who joined the search this year. “Thus far, it does not match samples currently in our genetics database, so it is not one of the readily known invasives. We are adding additional samples from other warmer water locations to our database for comparison.”

The U.S. Geological Survey, which tracks nonnative species found throughout the United States doesn’t have a record of the new ascidian either.

Despite these hurdles, researchers say they’ve already learned some important clues about this mystery sea creature – it doesn’t like the cold.

“The cold weather snaps in December and January seemed to have greatly reduced the abundance of the new sea squirt,” Walters said. “We are having fewer sightings now, and that’s a good thing. However, with warmer weather on the way, new individuals may be found again.”